1. Field of the Invention
The present invention relates generally to adjustable shims used with mold seals for injection molding of polymeric material to a shell.
2. Background of Related Art
For years, porcelain-cast iron mixtures have been widely used. However, one of the difficulties with porcelain-cast iron and enamelled fixtures has been their susceptibility to impact damage and their extreme weight which makes moving installation of large fixtures such as bathtubs and whirlpools, most difficult. While the porcelain-cast iron fixtures have the advantage of providing a very solid feel and high weight bearing capability, these drawbacks have made them less attractive.
Initial attempts by the industry to replace these porcelain-cast iron fixtures, have been to introduce lighter and more resilient component structures, however, this has not been without difficulty. Some of these included thin stainless steel fixtures which were lighter than the porcelain-cast iron fixtures, but did not have the solid feel or structural strength required for large articles such as bathtubs and whirlpool tubs. The early composite structures used in construction of such sanitary fixtures, had a plastic, hollow feel which would deform, crack, chip or delaminate when subjected to impact, thermal shock or the weight of a typical bather.
One successful solution to the above-mentioned shortcomings and drawbacks of prior art sanitary fixtures, is disclosed in U.S. Pat. No. 4,664,982 to Genovese et al., the disclosure of which is incorporated herein by reference as if fully set forth herein. U.S. Pat. No. 4,664,982 discloses a composite enamel steel fixture which has both the look and feel of the earlier porcelain-cast iron fixtures. The composite structure is light, has high structural strength, and resists delamination, chipping and denting due to impact or thermal shock. The composite enamel steel fixture is formed from a steel shell, which is typically formed from a blank by a series of stamping and punching operations. This shell is then enamelled often on both its finish surface and non-finish surface. As used hereinafter, the term "finish side" refers to the surface of the sanitary fixture with which a bather typically comes in contact during general use. The "non-finish side" refers to the underside surfaces of the sanitary fixture with which a bather typically does not come into contact. The enamelling process usually includes heating the steel shell to high temperatures and melting the enamel onto the shell surface. This heating and subsequent cooling often results in slight bowing and distortion of the shell. The enamelled shell is used as a part of a mold to form a layer of polymeric material by Reaction Injection Molding ("RIM") or by Reinforced Reaction Injection Molding ("RRIM") on the nonfinish side of the shell. An example of such a bathtub shell is illustrated in FIGS. 1, 2A, 2B, and 3 in particular. In FIGS. 2A and 2B, the inherent distortion contour formed along bottom edges 2A and 2B of the upper flange of shell 1 during manufacturing, is grossly exaggerated for purposes of illustration. The degree of distortion along the distortion contour is typically maximized along the mid portion of the sides of the shell. Distortion along the upper flange can be as great as 0.094 inches and is typically less at points farther away from the mid portion of the sides of the shell. The actual degree of distortion and warpage along the upper flanges of any particular sanitary fixture typically varies from one shell to another. In FIG. 3, the inherent distortion contour formed along the sides 3A and 3B of the upper flange of the shell 1 during manufacturing is also grossly exaggerated for purposes of illustration. The degree of distortion along this contour is also typically at a maximum along the mid portion of the sides of the shell. The actual dimensions of the distortion contour vary from shell to shell, but generally fall within a predictable range.
Commonly assigned U.S. Pat. No. 4,664,982 to Genovese, et al. and patent application Ser. No. 07/400,289 to Kuszaj, et al. now abandoned and refiled as Ser. No. 07/626,238 on Dec. 12, 1990 and now U.S. Pat. No. 5,049,443 both of which are incorporated by reference herein describe polymeric foam backed enamelled-carbon steel or stainless steel plumbing fixtures that are resistant to chipping, cracking, crazing, delamination or deformation when subjected to impact from either the finish or non-finish side. The use of the aforementioned composite mold structures results in fixtures which have the feel of porcelain-cast iron and enamel fixtures, high impact strength, and resistance to delamination. These composite structures possess excellent physical and mechanical properties as a result of the chemical bonding of the reinforced polymeric layer to the enamelled steel or stainless steel shell. Another approach was to replace the enamelled-steel shell with a polymeric-cosmetic surface layer and binding that layer directly to a foamed plastic substrate to provide a high impact strength, delamination-resistant structure. This approach is disclosed in commonly assigned U.S. Pat. Nos. 4,844,944 and 4,844,955 both to Graefe, et al., the disclosures of which are incorporated by reference herein. These approaches suffer from the same problems described above with regard to bowing, and warpage of the shell due to the irregularity in the shell from the manufacturing process.
Copending U.S. patent application Ser. No. 458,598, now U.S. Pat. No. 5,129,804 entitled "Mold Having An Insert For Molding Bathtubs And Method Of Molding Same" by Marsilio et al. filed on Dec. 29, 1989 and now U.S. Pat. No. 5,129,804, discloses an apparatus for molding polymeric material to the non-finish side of the shell. As disclosed by Marsilio et al., the steel shell is inserted within a female mold portion or receptacle having a molding surface, to form a cavity between the molding surface and the shell. In order to apply sufficient pressure to the shell during the molding operation, a male mold portion having a surface which substantially conforms to the finished surface contour of the shell, is urged against the finish side of the shell under high pressures using a mold press. In order to close off the cavity formed between the female mold portion and the shell, a sealing system is typically required for containing the polymeric material injected within the cavity under high molding pressures.
In a proposed sealing system employable in the above-described molding apparatus, a urethane coating is molded onto the male mold portion to protect the finish side of the shell. This protective urethane coating is formed on the undersized surface of the male mold portion. Urethane, for example, is injected between the cavity formed by the undersized surface of the male mold portion and the finish side of the shell. The urethane polymerizes and cures, forming a protective surface which coats on the male mold portion. This protective surface contacts the upper flange of the shell and a portion of the female mold, sealing off the molding cavity formed between the non-finish side of the shell and the female molding surface. This proposed sealing system suffers from several significant shortcomings. In particular, since the seal is cast as part of the protective urethane surface coating the male mold portion, it is not replaceable. Since such seals typically wear and deteriorate over repeated molding cycles and need to be replaced over time, such sealing systems are not desirable. Also, due to variations in the shape of the shell, particularly near the upper flange portions which contact the seal, due to the manufacturing operations described above, the shape of the molded seals may need to be varied. Accordingly, it is extremely difficult and often impossible to form an adequately sealed molding cavity into which the polymeric material can be introduced under adequate molding pressure. Consequently, the polymeric material flows across and beyond the seal, often damaging the finish surface of the shell, or adhering to the surface of the female mold.
Another proposed sealing system used in molding bathtubs is disclosed in U.S. Pat. No. 2,841,823 to Van Hartesveldt. It discloses a molding apparatus for low pressure compression molding of laminates useful in fabricating large bulky objects such as boats or bathtubs. The mold includes an L-shaped baffle anchored in an upper molding block, and a lower molding block having a U-shaped channel which faces the L-shaped baffle. An inflatable hose is located in the U-shaped channel. To form a seal, compressed air is introduced into the hose, causing it to expand and engage the L-shaped baffle. The mold sealing system, however, suffers from a number of significant drawbacks. In particular, the inflatable hose is only maintained in the U-shaped channel when pressed against the L-shaped baffle. Also, the inflatable hose may become dislodged from the U-shaped channel when the L-shaped baffle is lifted from the lower molding block.
U.S. Pat. Nos. 4,732,553 and 4,626,185 disclose an apparatus for molding gaskets around the periphery of a window. They often include fluid filled bladders which are located in both the upper and lower portions of the molding apparatus. Seals rest above the bladders within seal grooves. The inflatable bladders within the seal groove adjust the height of the seal to engage the glass surface which is being molded. These seals and bladders are designed to contact a perfectly uniform glass surface on both of its sides, and are not designed for compensating for variating in the shape of a shell by the use of a seal engaging only one surface of the shell being molded. Additionally, these seals are maintained in the groove by adhesives and therefore are not easily released from the seal groove.
Generally of interest is U.S. Pat. No. 4,394,022 to Gilmore which disclose an annular reusable sealing assembly for providing high pressure seals between containment surfaces, such as pipe sections or access port valves of a nuclear reactor. The seal assembly includes a U-shaped ring structure which has a containment surface and a seal which is positioning below the pipe section or access port valve to be sealed. A planar ring is positioned on the bottom of the inside of the U-shaped ring and a plurality of ring seal wedges with inclined surfaces cooperate with a plurality of bottom ring wedges that are positioned on top of the planar ring. Threaded posts connect the bottom ring wedges to the ring, so that when the bottom ring is rotated the bottom ring wedges slide against the ring seal wedges, causing the seal to be either raised or lowered, depending on the direction which the bottom ring is rotated. The mechanical system of Gilmore can only raise or lower the entire seal, it cannot lift one segment of the seal while lowering another segment to adjust the seal to a particular contour, as required in molding shells for making sanitary fixtures, such as bathtubs and whirlpool tubs.
In response to the problems associated with the prior art sealing systems, an alternative sealing system was proposed by the inventors, herein. In this proposed sealing system, a seal groove is formed in the male mold portion above the upper flange of the shell and adjacent the cavity formed between the underside surface of the shell and female mold, when the molding apparatus is in its closed position. In the seal groove, segments of urethane material are inserted end-to-end to form a seal which is retained in the male mold portion by an overhanging edge projecting from the protective urethane surface on the male mold portion. While this proposed sealing system provides a seal that can be replaced, however not without some difficulty, it nevertheless suffers from several significant shortcomings and drawbacks. In particular, the overhanging edge projecting from the protective urethane surface fails to adequately retain the seal in the groove of the male mold portion during demolding operations. Also, this system is incapable of establishing an effective seal along all engaging surfaces of the shell, due in large part to the bowing and distortion in the shells from the manufacturing processes.
In view of the shortcomings and drawbacks of proposed prior art methods and apparatus for effecting a seal between the shell and molding surface of a mold receptor used for molding polymeric material to the surface of the shell, there is a clear need to provide a type of sealing system that overcomes the above-described shortcomings and drawbacks.
Accordingly, it is an object of the present invention to provide a sealing system for molding polymeric material to the surface of a shell, in which the height of the seal in can be selectively adjusted along the length of the groove in the mold in order to form a perfect seal along all engaging surfaces of the shell and mold.
It is another object of the present invention to provide such a sealing system in which the height of the seal along the length of a seal groove in the mold, can be variably adjusted to accommodate the distortion contour along the upper flanges of sanitary fixture shells caused as a result of operations employed in the manufacture of the shell.